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- https://chat.fhir.org/#narrow/stream/snomed/subject/SRT
- https://chat.fhir.org/#narrow/stream/terminology/subject/SNOMED.20srt
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Response from Linda Bird
I don't think we should be changing the SNOMED URI standard to expand its scope to non-SNOMED CT code systems (such as SNOMED RT or SNOMED 3.x), which are currently explicitly excluded from scope. These old SNOMED code systems were formally deprecated last year and are now no longer supported - so it would be a bit odd to decide now to expand this standard to formally support their use. The decision to deprecate this code system was made by the GA, and had the clinical support of the World Association of Societies of Pathology and Laboratory Medicine. My understanding is that the deprecation policy places the obligation on the sender to use the simple map we have provided to map the codes to SNOMED CT. Any move from us that may be seen to be contrary to this decision may be questioned.
In addition, the SNOMED URI standard has been specifically designed to identify SNOMED CT artefacts, and therefore the pattern http://snomed.info/id/{sctid} is specifically used for sctids. The pattern http://snomed.info/sct/{sctid} identifies a specific SNOMED CT edition .... and therefore it would not be consistent to use http://snomed.info/srt/{srtid} to identify a SNOMED RT id.
And finally, SNOMED RT identifiers (published in January 2001) are SCTIDs, and were re-released in the January 2002 version of SNOMED CT - so they can actually be treated just like SNOMED CT ids, because they are valid SCTIDs in current SNOMED CT release (even though some of them may now be inactive). The only old SNOMED identifiers that cannot be treated like SNOMED CT ids are the SNOMED 3.x identifiers ... because these are a different style of identifier. The SNOMED RT release included a column containing these legacy SNOMED 3.x identifiers (much like SNOMED CT provides a map to these) ... but these are not SNOMED RT identifiers. Also, all concepts that had a SNOMED 3.x identifier (with the exceptions that follow) also have a SNOMED CT identifier, so this map should be reasonably simple. The only exceptions to this are (1) There were some concepts in SNOMED 3.x (and possibly SNOMED RT) that were removed by CAP due to an I.P. challenge from another code system provider) (2) Some local/national codes may have been added using the SNOMED 3.x format (e.g. additions were made in the French translation of SNOMED 3.x).
I notice on this page - http://build.fhir.org/terminologies-systems.html - that FHIR uses hl7/fhir URIs for a range of different code systems that don't have URIs - e.g. http://hl7.org/fhir/sid/icpc-2 and http://hl7.org/fhir/sid/ndc. Perhaps the same can be done for SNOMED 3.x and other deprecated code systems? For example http://hl7.org/fhir/sid/s3x. The only reason that this should be necessary for SNOMED RT is if an implementation uses SNOMED RT extension codes ... but if so, then something like http://hl7.org/fhir/sid/srt could be used. The documentation should also clearly indicate the deprecated status of these code systems. It may also be useful to add something to the 'Using SNOMED CT with FHIR' page on the FHIR website that explains some of this history, including the deprecated nature of these code systems.
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